1. Field of the Invention
The invention is directed to determining the effectiveness and sufficiency of thermal insulation in barriers such as walls, floors, and ceilings.
2. Description of the Prior Art
Heat flows between the interior of residential structures and the exterior by means of conduction, convection and radiation. Heat loss from the structure during the heating season and heat gain during the air conditioning season are economically and physiologically undesirable. This flow is impeded by the addition of thermal insulation placed between the inner and outer walls, in the ceilings above the heated space, and, occasionally, in the floors under it.
Many of the residential dwellings in the United States have less insulation than that considered economically desirable at the current cost of heating or cooling, or have gaps in the existant insulation at various locations, e.g., around windows. It would be desirable for the owners of such dwellings to be able to identify such locations of missing insulation, or to assess the efficacy of that insulation which is present. From such a survey, the owner can determine the need for adding insulation to reduce heat flow.
Several measurement devices exist for assessing the performance of installed residential insulation. These devices typically work on one of two principles. The first type is a heat flow meter in which two termperature-sensitive elements are placed on either side of a suitable, known thermal resistance. This assembly is placed in contact with the surface to be measured, and the temperature difference across the known thermal resistance is measured by means of electrical or electronic circuitry. The heat flow through the known resistance, and hence, through the surface whose heat flow is to be measured is, therefore, determined. A practical equipment for this measurement is marketed under the name of Model HA-100 HEATPROBE.RTM. System by International Thermal Instrument Company, Del Mar, Calif. The complexity and precision of this equipment would not make it suitable for individual residential ownership or use. Hence, the cost of its use by a suitably trained individual would inhibit its widespread application.
The second type of equipment usable for insulation performance survey makes use of the fact that any object warmer than absolute zero temperature emits radiation whose quantity is dependent on its temperature and emissivity. A number of sensors of this radiation are in existence, and when coupled with a suitable optical system and electronic amplification, a two-dimensional optical "picture" of the temperature distribution of the surface can be obtained. A practical equipment for this measurement is marketed under the name of AGA THERMOVISION.RTM. Systems by AGA Corporation, Secaucus, N.J. This equipment is also complex and costly, and would, therefore, be used only by a trained individual.
A need remains for an inexpensive, easily usable device for determining the effectiveness of thermal insulation.